


Crossing the Line

by estelraca



Category: Kamen Rider Decade
Genre: M/M
Language: English
Status: Completed
Published: 2014-09-08
Updated: 2014-09-08
Packaged: 2018-02-16 15:57:37
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,662
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2275761
Author URL: https://archiveofourown.org/users/estelraca/pseuds/estelraca
Summary: <blockquote class="userstuff">
              <p>Kaitou comes to the Hikari Photo Studio, grappling with a decision that he made; Tsukasa helps him come to terms with at least a bit of the world's complications.  Written for Kazuraba-Kouta's End of Gaim Songfic Challenge.  Vague spoilers for the Showa vs. Heisei Riders movie.</p>
            </blockquote>





	Crossing the Line

**Author's Note:**

> This story was written for Kazuraba-Kouta's End of Gaim Tokusatsu Songfic Challenge. Vague spoilers in this for the Showa vs. Heisei Riders movie because I actually really like where that takes Tsukasa's character arc. The song that's used in the introduction and for section breaks is Vienna Teng's "Enough to Go By", one of my all-time favorite songs. It can be listened to on YouTube at: watch?v=rVw8oWrHKEQ

_I'm at your back door_   
_With the earth of a hundred nations in my skin_

_You won't recognize me_   
_For the light in my eyes is strange_

Kaitou comes in through the window.

That should have been Tsukasa's first clue that something was different—that something was wrong. Slowly but surely over the last three years Yuusuke and Natsumi have been prodding and poking Kaitou into using the front door to the Hikari Photo Studio instead of sneaking in through whatever random not-entrance he decides looks the most appealing. It's a battle that Tsukasa has watched with lazy interest, never really taking sides—he doesn't care if Kaitou wants to come in through the front door or the back door or one of the windows or even materialize inside one of their rooms. The only time he's really taken exception has been when Kaitou wakes him up or appears somewhere that Tsukasa doesn't want him, such as in the shower without notice. ( _With_ notice or when Tsukasa has dragged him there is just fine; without notice is an interruption, a ruining of the mood, and Kaitou seems, frustratingly, to understand how much that _annoys_ Tsukasa.)

This time, though, he comes in through the window. It's the draft that wakes Tsukasa—he had left all the windows closed and no fans running, so the trickle of cold air that pulls on his bangs tells him that something important has changed in his environment.

Maybe one day he won't wake for things like that. Maybe one day he won't be aware, even in his sleep, of changes in temperature and scent and air movement and sound that could indicate someone trying to kill him. (Someone trying to kill Yuusuke or Natsumi, usually but not always because they are associated with him.)

Maybe, but that day is far in the future, and tonight the stirring of the wind is enough to wake him.

That means he has his eyes slitted open to watch Kaitou drop into the room. The thief's steps are feather-light, making no sound as he slithers off the sill and around the clothes Tsukasa flung there earlier to stand on solid ground. For several seconds Kaitou stays perfectly still, nailed in place, his hands hanging at his sides. There are streaks of soot and ash covering his jacket, a tear across the front of his black shirt, and the knees of his jeans are damp where he knelt in something liquid recently.

Kaitou's eyes stare downward, at a spot on the floor halfway between the bed that Tsukasa is lying in and the one that Yuusuke isn't occupying tonight. He raises his arms slightly, hands hanging limply on his wrists, takes a step forward... and drops to the ground, forehead buried against his knees as he curls into a defensive huddle.

Tsukasa is off the bed before he thinks about moving, kneeling in front of Kaitou, reaching out to touch his shoulder.

Kaitou raises his head slowly, and his eyes seem to shimmer in the dim reading light that illuminates the room—the light Tsukasa didn't turn off, falling asleep instead on the book that Natsumi insisted he try reading. Are those _tears_ in Kaitou's eyes? Surely not. Kaitou doesn't cry—not in front of Tsukasa.

"Tsu—" Kaitou's breath comes out in a low whisper, and he clears his throat, licks his lips, and tries again. "Tsukasa. Morning."

"Evening, actually." Tsukasa's hands on Kaitou's knees gently force the man into a more natural seated position. Whatever the liquid is on Kaitou's pants, it's not blood, at least. There seems to be little if any blood on the thief, actually, and Tsukasa breathes a silent sigh of relief. He is not going to have to explain to the rest of their family why he has Kaitou's corpse in his room. (He isn't going to lose Kaitou, a horrifying idea... though it is always strange to think of it that way—losing Kaitou, when Kaitou is the freest of all of them, flitting where he will but always returning home often enough to be unequivocally _theirs_ —unequivocally _Tsukasa's_.) "Not that I would expect a sneak-thief who's only interested in his own gain to remember what time of day it is in a new world."

Kaitou's breathing hitches, and his eyes meet Tsukasa's. Blaze into Tsukasa's, a fierce, terrible light glowing within them as Kaitou's hands twitch.

Does he want to grab Tsukasa? To strike him? To shove him away? To hold Tsukasa in place?

Tsukasa doesn't know. He doesn't understand, and that's a frustratingly, disconcerting feeling, because he usually understands Kaitou. He can usually play Kaitou as easily as Kaitou plays others, though he has been better, since the War, gentler about the ways in which he uses people—even people who will just as readily use him. Reaching out slowly, he gently takes both of Kaitou's hands in his own, the callouses familiar under his fingers. He isn't surprised to find that Kaitou's hands are shaking. "Kaitou—"

"Where are Natsumi and Yuusuke?" Kaitou talks over Tsukasa.

For a moment Tsukasa considers not answering, but the mental echo of Natsumi's warning voice makes him sigh and reconsider. "They're both out for the day—spending time with Godai Yuusuke and Ichijou Kaoru. I didn't feel like going with them."

"Oh." Kaitou nods, and his trembling has slowed. Then he raises his head again, and once more his eyes shine with barely-restrained emotion. "How many worlds have you been to, Tsukasa?" The question comes out in a hot rush, the shaking in Kaitou's fingers increasing, trying to transmit itself to Tsukasa's body.

"I..." For a moment, on reflex, he begins counting—the worlds that were cataloged and named and numbered by DaiShocker, a world for every Rider he has met, a world for himself and Sayo, a world for Natsumi, and does the photo studio count as a tiny, precious, priceless world—but he knows that there are too many for him to possibly get it right. "I have no idea."

Kaitou laughs, a breathy, rushed sound like butterflies beating themselves against a cage wall. "I've seen one thousand, three hundred and eighteen worlds in the last five years. I know. I keep track. I've got... I've got a record. So I know where I've been and what I've done and where everything I've acquired comes from."

Tsukasa finds himself repeating the numbers in a low whisper, trying to imagine what they mean. How often has Kaitou jumped place to place, to see that many worlds?

How does that compare to the number of worlds Tsukasa has seen?

How does that compare to the worlds that Tsukasa has seen and _remembers_ versus those trips for DaiShocker that are still a hazy blur, memories fragmented and scattered by the Riders as they fought back against extinction?

Shaking his head, Tsukasa focuses his gaze again on Kaitou. Right now, Kaitou is what matters, because right now Kaitou is the one hurting. "That's a lot of worlds."

Kaitou nods, a stiff, shivery movement. "A lot of worlds. More than I ever imagined could exist before I met you... before you changed me. Changed everything."

Tsukasa swallows back the defensive words that want to come. He does not protest when Kaitou or Natsumi or Yuusuke accuse him of changing them—how can he protest something that is undeniably true, even if Tsukasa doesn't always mean to be the catalyst that he is.

"And in all those worlds, Tsukasa. In all those beautiful, wonderful, terrible, _boring_ , _unbelievable_ worlds, I've kept one thing constant. One thing." Kaitou's voice is once again a strangled whisper. "I've kept myself. I've kept the promise I made—gods, you probably don't even... I've been a thief. I've been a thief and a liar and an agent of chaos and a thousand other things to a thousand different worlds. But I've never, ever been a hero."

That's not true. Tsukasa knows that's not true because he's seen it—he's seen Kaitou save people, time after time. He's seen Kaitou's soul flayed open, his heart bleeding on the soil of his home-world. He's heard tales of Kaitou thieving to protect, thieving to defend, thieving so that worlds and Riders can continue on. He's _seen_ Kaitou save people that would have died...

And he's seen Kaitou put people in danger who didn't need to be. He's seen Kaitou summon monsters and throw temper tantrums and risk worlds just because he _can_ , just because he's hurting, just because he is, as he so eloquently put it, an agent of chaos.

And he sees Kaitou's eyes, glittering across the scant distance between their bodies, and knows what it is that's happened. "Except today. You were a hero today."

Kaitou's head falls forward, buries itself on Tsukasa's shoulder as the shivering takes over again. His voice is barely audible as he whispers, "I was a hero today."

_It was years ago, God knows_   
_When you strained to tell me your whole truth_   
_That you were not mine to save_   
_That you could not change_

Kaitou rests his head on Tsukasa's shoulder, a motion that has become familiar, and tries to figure out how he ended up being a hero again.

Him, the man who couldn't even save one person before.

Kaitou had tried, for the first few weeks that he was at DaiShocker, to explain to Tsukasa why the things that he did were horrible.

They were disjointed explanations. He knew that—he _heard_ it, every time he opened his mouth, the way his tongue stumbled over the recriminations and remonstrances.

_You shouldn't torture people, Tsukasa._ That was the first point that Kaitou tried to make a stand on. It was a simple point, really, something that he thought should be self-evident, should take no long explanation that he didn't have the heart to give.

_They have information that we need._ Tsukasa's face had contorted in a mask of confusion. _Information that's necessary to understanding how to bring the worlds into a safe equilibrium. Information on the people fighting against us. And they won't share._

_They won't share._ The absurdity of that statement coming from the man who wanted to rule over the multi-verse had stunned Kaitou into silence—a silence that Tsukasa had apparently taken as acquiescence to continue.

_You can go wait in your room._ The dismissal had been almost kind, a wave of Tsukasa's hand that sent him away, locked him out of Tsukasa's consciousness.

Kaitou had fled, not wanting to hear the screams or the deafening silence that would follow them.

He should have argued more. He should have fought harder about everything—should have tried to impress upon Tsukasa how important life was, how terrible it was to hurt another, how everyone had a right to their own body and soul.

He _did_ fight, in tiny bits and pieces. He told Tsukasa that murder was wrong, that torture was wrong, that a _dictatorship_ was wrong...

But Kaitou grew up in a world where the most important rule was to preserve the peace and serenity of the community, and he developed programs that fed people to an inhuman monster as brainwashed slaves, and he watched his own brother's soul disappear under the onslaught.

How was he supposed to teach a teenage megalomaniac how to be a better person when he was a rather terrible one himself? How was he supposed to explain how the world was supposed to be a good place where people helped each other and protected each other when he couldn't protect anyone?

How was he supposed to counter a lifetime of monsters telling Tsukasa that he was special, that he was unique, that he was destined to rule the world, when he had no hard evidence to the contrary?

The longer he stayed with the young godling the less he cared about what Tsukasa did. The less he cared about what would happen to his world, numbness replacing the debilitating agony in his chest and head. The less he questioned Tsukasa on what happened in his labs or how his monsters were made or what his plans were for the worlds once they were conquered.

He couldn't become what Tsukasa was, though. He couldn't become a monster without malice. He knew too much—had seen too much, been too much already—and the monster that he was becoming knew a cruelty that Tsukasa could only dream of. (That Apollo Geist and Shadow Moon could only dream of, and Kaitou enjoyed it, by the end of his stay with DaiShocker, dancing in a battle of wits and politics with the men who thought they would own the universe. That was part of why he knew he had to go—knew he had to do what he could to preserve the malice-less monster, to ensure the maybe-god who had saved him would get a chance to continue on.)

Perhaps he should have stayed.

Perhaps he should have fought harder, because Tsukasa _could_ have learned.

Natsumi and Yuusuke showed that. It took time and effort and more pain than Kaitou thinks he could have born, but the two of them took Tsukasa and made him something even more beautiful than the impossible monster that first dragged Kaitou through the doors between worlds.

A man who is now kneeling in front of Kaitou, holding him, meeting his frantic panic with a calm, cool incomprehension.

"I _can't_ be a hero, Tsukasa." The words tumble over themselves, tripping on his usually-talented tongue. "It's not _me_. It's not—"

Tsukasa's right hand moves, snake-fast Rider reflexes, and comes to rest against Kaitou's mouth. "Tell me what happened."

Drawing a breath that shudders despite his best efforts, Kaitou closes his eyes and waits for Tsukasa to move his hand before speaking. "I went to a new world. There were two young Riders—they couldn't have been more than eighteen, nineteen. One was a boy, and his eyes... they were like Yuusuke's eyes, so full of fire and hope and light. The other was a girl, and when I told them I couldn't help, that I was just a passing-through Kamen Rider—"

A small, pleased noise escapes Tsukasa's throat as his mouth turns up in a slight smirk.

"— _not_ that I was copying you, it was just a good line at the time." Kaitou glares at Tsukasa, and is pleasantly surprised to find that his voice doesn't shake at all. He suspects that won't last for long, though. "When I told them that... her expression... She didn't look anything like Natsumi before that, but the way her face twisted, the way her mouth pouted and her eyes were so sad... like she knew before I spoke what I would say but she hoped anyway and even if I wouldn't help them they would throw themselves at the problem..."

_Damn_ his body for reacting like this, for shaking like this, for making him weak like this.

Tsukasa's lips press gently against his neck—against his throat, and somehow the pressure frees the words so he can speak again.

"There wasn't anything I wanted there. Nothing to steal. Nothing to gain. Just the light in his eyes and the smile that I knew she was capable of, and though I should have left..." He swallows, leaning forward as Tsukasa's arms snake around his back. When Tsukasa's lips press themselves to the other side of his neck, the words once more tumble out. "I could have gotten you _and_ Yuusuke and Natsumi. I could have gone to any of the other Rider worlds—"

"Not quite." Tsukasa's tongue laps against his chin, raising his head. "Terui still wants to arrest you; Hikawa might also arrest you just on principle."

"All right, _most_ of the other Rider worlds... I could have sent them... someone else." Kaitou shudders. "Anyone else. A real hero."

_Carry the weight_   
_I'll carry the weight of you this time_   
_Carry the weight_   
_I'll carry the weight of you_

"A real hero." Tsukasa tries out the taste of the words in his mouth, his hands massaging gently against Kaitou's tense shoulder blades. "What, precisely, is a real hero?"

"You know." Kaitou glowers at him, and there is more of _Kaitou_ in the expression, less of the panicked, running man who stumbled his way into Tsukasa's room. "You _live_ with two of them. You've _killed_ enough of them—"

Kaitou cuts his words off, but too late. Tsukasa's hands still, and it takes him a moment to find his voice again. "I suppose you'd know, since you watched me do it."

"Touche." Kaitou closes his eyes, a small, tired smile playing at the corners of his mouth. "And I'm sorry. I shouldn't have... I didn't mean to do that."

"You and I are good at pushing each other." Drawing a slow breath, Tsukasa tries to bury the old, ugly wounds once more. "But there's no one else here right now—no one to intercede, no one for us to turn on. Just you and me, Kaitou. Just two men who know what it means to be a hero because we've observed it from the outside."

"Me more than you, I think." Reaching over, Kaitou runs a hand along Tsukasa's jaw, toys it through his loose, shaggy hair. "At least this world wasn't cruel about your hairstyle."

"You should have seen me a few hours ago." Tsukasa grabs hold of Kaitou's wrist, nips gently at the skin in a way that makes Kaitou shiver. "I swear the more I annoy Ichijou, the worse my hair looks when we come here. Showers are wonderful things. But you're not getting out of this conversation that easily."

"Tsukasa..." He isn't shaking any more. Now that he's shared what's bothering him, let loose the words and contradictions that were choking him, he can breathe normally again. He even feels _silly_ , kneeling clothed on the bedroom floor while Tsukasa sits across from him in nothing but boxer shorts, a faint ink impression showing on his right cheek where he was sleeping on a book.

"No. You woke me up, you're going to talk about this until you can think about it without hyperventilating."

"This is silly." Kaitou squirms, but he'll have to honestly fight Tsukasa to get out of the man's hold, and he's not quite at that level of embarrassment. Especially when Tsukasa's teeth nip once more at his wrist. "There are better things we could do with our night."

A grin that has more in common with the Destroyer of Worlds that Kaitou first met than with Kamen Rider Decade slides onto Tsukasa's face. "We could always multitask."

"Well..." Kaitou shivers, the first time in hours that it's been a pleasant sensation, as Tsukasa's hands dive beneath his shirt. "If you're managing to keep me entertained so I don't want to leave, I suppose there's nothing I can do about what you say."

_Would it be enough to go by_   
_If we could sail on the wind and the dark_   
_Cut those chains in the middle of the night_   
_That had you pulled apart_

He isn't gentle with Kaitou.

He can be—he has been, when the time called for it.

Now isn't that time, though. Now Kaitou is drowning in contradictory truths, the past that they can't escape coloring the future that they don't dare to dream of, and he needs Tsukasa to be both.

He needs Tsukasa to be the past, to be the boy-man-god who pulled Kaitou down onto a prisoner's cot and took his first kiss and his virginity without realizing how important both were. (He spent days searching for that memory, trying every trick he could to sneak up on it, to steal it out of the gray-white haze that still shrouds some of his past. He needed to know if Kaitou gave himself willingly, needed to know if that was one more sin from his past, and he was crying in relief and bleeding from his nose when Yuusuke finally tracked him down.)

He needs Tsukasa to be the future, to be a world where Kaitou is whole and hale, someone that can be held down and owned and loved without fear of breaking.

They speak in little snatches, traded lines of point and counterpoint.

"You can be a hero."

"Says the man who was a monster."

"Says the man you called a hero last week."

"You risked yourself to save a damn _ghost_ and _ah—_ "

They speak with their bodies, Kaitou allowing Tsukasa to take him first. (He doesn't allow Tsukasa to tie him, but that's all right because Tsukasa doesn't want, right now, to be more of the Destroyer than he always will be.)

They use words when actions would be unclear, when actions could be interpreted in ways that would drown out their true meaning.

"You can make worlds better."

"By killing a man who could have been _you_ , oh evil mastermind?"

(There is no one like Tsukasa in all the worlds. They know, because they have looked, have found versions and variants of everyone but Tsukasa. That is not what's really in question here, though.) "Could he? Could he really have been me?"

"No." There had been no hesitation in the answer, though Kaitou gasps in pleasure a moment later. "There was hatred and glee in his eyes as he killed. Some people even Yuusuke couldn't save."

Tsukasa should argue that, maybe. He should argue that he wasn't special, that he was just lucky, that there is no one who doesn't have a glimmer of hope of salvation in them. Yuusuke would argue, maybe. Tsukasa is silent, though. (There is a line, somewhere, a line between salvageable and not, a line that Tsukasa has danced with but not crossed. It is the line between the Grongi and the Linto, a line the Fangire and the Orphenoch straddle with uneasy grace, and it is sometimes very, very hard to see.)

"They aren't saints." Tsukasa pants out the response, trying to match Kaitou's rhythm, to tease the thief over the edge before he himself falls.

"Uh huh." Kaitou's response is utterly disbelieving.

"Yuusuke snores." Tsukasa gasps. "And Natsumi uses that damn laughing pressure point just for fun sometimes."

"They're both more saints than either of us."

There is no arguing with that, so Tsukasa just focuses on what he's doing, ensuring both of them enjoy it.

When they've both climaxed Tsukasa returns Kaitou's trust, allowing Kaitou to tie him hand and foot and blindfold him. It is an act that Kaitou respects, and Kaitou's words and hands are gentler than they would usually be.

"I _like_ being a thief."

"So keep being one."

"How can I be a thief _and_ a hero?"

"By looking at who's hurt and how much. Saving worlds doesn't mean being a saint."

"Except when it does."

Tsukasa smiles into the darkness, knowing who Kaitou is thinking of. "Except when it does."

"Not you and me, though." Kaitou's hands are gentle as they trace symbols on Tsukasa's chest—symbols of friends, symbols of worlds, symbols of who and what they are.

"No, not you and me."

They don't talk again in words after that, but Tsukasa thinks he's said enough to make his meaning clear.

_Would it be enough to go by_   
_If there's moonlight pulling the tide_   
_Would it be enough to live on_   
_If my love could keep you alive_

They shower and dress and jump out the window into a portal of Kaitou's creation, the thief laughing as they drop.

The world they go to is beautiful, the sky a blazing font of stars, no lights on the ground that Tsukasa can see.

"I never found people here." Kaitou pushes his way through a jungle of chest-high grass, heading for a rocky outcrop that Tsukasa can just make out as a slash taken out of the sky. "I've found the occasional ruin, so people _were_ here, but now..."

Now there is the not-silence of buzzing insects and howling canids and cheeping amphibians. Now there is light that has nothing to do with the light that Tsukasa is used to, a distant, shimmering, indescribable beauty.

What would this world look like from space?

What does it mean, a world devoid of human life?

Kaitou's hand stretches back, grabs Tsukasa's in a firm grip, and leads him forward.

They spend a few moments slapping bugs from their clothes before settling down against a rock that has one face worn suspiciously smooth.

Tsukasa tries to study Kaitou's face, but it's impossible to see in the shivering starlight. Instead he waits, certain that Kaitou had a reason for bringing him here.

"It's dangerous."

Tsukasa raises one eyebrow, realizing too late that Kaitou will have as much issue seeing him as he has seeing Kaitou.

The thief continues, anyway. "Being a hero... that's how I almost destroyed myself once. That's how Yuusuke _breaks_ himself again and again. That's why Natsumi has scars all over now."

"Yuusuke keeps doing it, and Natsumi's happy to stand beside him." Tsukasa tilts his head back, watching for shooting stars.

" _You're_ happy to stand beside him. You... you've become..." The silence stretches, but it isn't uncomfortable. "You were part of a coalition of heroes that straight-up saved a world not that long ago. _You_. The Destroyer of Worlds, the Killer of Riders... you're really one of them now. You're not a saint—I don't you ever _could_ be—"

"I don't think I'd ever _want_ to be."

"But you're really a hero now. In your own right, on your own two feet." Kaitou sighs, his profile curling in on itself. "Maybe that's why I had to try it again, too. I can't let you get too far ahead of me. But I'm not like you. I'm not just now learning to be a hero. I've been a hero before. I've given my soul to a cause and watched it all explode and had to glue the tattered fragments back together. And I don't know if I could do it again."

"You can." Tsukasa reaches out, resting a hand on Kaitou's knee. "I've done it; you've done it. We can both do it again, if we need to."

"I don't want to die." Kaitou makes a sound that could be a laugh or a sob. "I don't want _you_ to die. And heroes have this tendency of dying..."

"You brought me back from the dead." Tsukasa tightens his hold. "You brought me back from _non-existence_ , made me again from shards and splinters of memory because you couldn't let me go... didn't _want_ to let me go. You saved me when the universe said I shouldn't exist. What was that if not the act of a hero?"

"A selfish act. An act of self-preservation, because I keep comparing myself against..." Kaitou gives a brief, choked chuckle. "It wasn't anything heroic."

"It was." Tsukasa pats Kaitou's knee. "But you don't have to admit it if you don't want to."

"You don't get to redefine words just to make your point. Heroes save _worlds_ , not..."

"Not individuals?" He suspects Kaitou bit back something more scathing, something like _monsters_ or _murderers_ , but he'll run with what he likes. "What do you think worlds are made of, Kaitou?"

Silence, waiting, full of potential, and Tsukasa once more reaches out to touch Kaitou, needing to feel someone else alive in the universal darkness.

"Could you promise me we'll survive, Tsukasa?"

It's a child's question. It's a question Kaitou knew the answer for before he ever met Tsukasa.

"I can promise that I will do everything I can to keep you alive." Tsukasa leans forward, pressing a kiss to Kaitou's cheek. "I can promise that if love and desire can keep us alive, we'll last forever, Daiki, whether we're heroes or not."

Kaitou leans back, molding himself into Tsukasa's embrace, and heaves a deep sigh. "I guess... for this unlikely hero, at least... that'll be enough."


End file.
